The present invention relates generally to improvements to the general class of clutches known as pawl and ratchet clutches. In U.S. Pat. No. 3,810,210 a self-processing camera is described in which upon actuation of the shutter release member a film unit is exposed and a leading edge thereof advanced into the nip of a pair of opposed pressure rollers. The passage of the film unit through the pressure rollers uniformly spreads a developer solution over the image recording portion of the film unit and drives this portion of the film unit from the camera. The patent discloses that to advance the film unit into the nip of the pressure rollers a reciprocable feeder unit may be used which includes a claw-like member that engages the film unit and moves the film unit towards the pressure rollers. The motivating power for the claw is provided by a motor that is coupled to the feeder unit through a pawl and ratchet clutch. The presence of a clutch is desirable since the pressure rollers are directly driven by the motor through suitable gearing and require that drive be provided to them for a time longer than that required to be provided to return the fingers to their initial position. The clutch, therefore, may be uncoupled at an appropriate time in the drive cycle so that continued drive to the pressure rollers can be provided without further disturbing the feeder unit.
As known in the prior art, a pawl and ratchet clutch includes a ratchet wheel that is keyed for example to a rotating input drive and a pawl that is coupled to an output mechanism, such as a gear or cam, for rotation with such mechanism. The pawl is pivotably supported on the output mechanism so that it may pivot into and out of coupling engagement with the ratchet wheel and thereby selectively couple the rotary input drive to the clutch output mechanism. In a self-releasing pawl and ratchet clutch a surface on a clutch release finger may be located to block the path of the pawl when it is rotated with the ratchet wheel and thereby uncouple the pawl from the wheel after a desired period of coupled rotation of the two members. While this type of clutch operates generally satisfactory in a mechanical sense a problem which may occur with such clutches is the generation of noise created by the wiping of the teeth of the rotating ratchet wheel against the uncoupled pawl.